OAuth2\OAuth2::grantAccessTokenRefreshToken PHP Method

    protected function grantAccessTokenRefreshToken(IOAuth2Client $client, array $input)
    {
        if (!$this->storage instanceof IOAuth2RefreshTokens) {
            throw new OAuth2ServerException(self::HTTP_BAD_REQUEST, self::ERROR_UNSUPPORTED_GRANT_TYPE);
        }
        if (!$input["refresh_token"]) {
            throw new OAuth2ServerException(self::HTTP_BAD_REQUEST, self::ERROR_INVALID_REQUEST, 'No "refresh_token" parameter found');
        }
        $token = $this->storage->getRefreshToken($input["refresh_token"]);
        if ($token === null || $client->getPublicId() !== $token->getClientId()) {
            throw new OAuth2ServerException(self::HTTP_BAD_REQUEST, self::ERROR_INVALID_GRANT, 'Invalid refresh token');
        }
        if ($token->hasExpired()) {
            throw new OAuth2ServerException(self::HTTP_BAD_REQUEST, self::ERROR_INVALID_GRANT, 'Refresh token has expired');
        }
        // store the refresh token locally so we can delete it when a new refresh token is generated
        $this->oldRefreshToken = $token->getToken();
        return array('scope' => $token->getScope(), 'data' => $token->getData());
    }